Pyrethroid insecticide is a kind of biomimetic pesticide with high efficiency, wide insecticidal spectrum, low toxicity and safe to humans and animals. It thus has been widely used and has become one of the major products of insecticides. The primary pyrethric acid series, such as allethrin, tetramethrin, phenothrin, furamethrin, and the analogues, play an important role in public hygiene as well as in controlling vector insects; the development of dihalopyrethroids with high efficiency and low toxicity, such as Cypermethrin (M. Elliott et al., Ger. P2326077, 1974), Deltamethrin (M. Elliott et al., Nature, 248, 1974, 710), and the analogues, is a milestone in the history of pesticides, and the presence of two chlorines atoms on the double bond makes pyrethroids to possess better light stability in comparison with chrysanthemumate pertaining to the primary pyrethric acid series and thus has been widely used in the protection of agriculture plants.

Deltamethrin is particularly valuble, which was synthesized by Elliott in 1974 based on the study of the chemical structures of natural pyrethrins. It is a type II α-cyano-containing pyrethroids class bionic pesticide, and is one of the most efficient synthetic pyrethroid insecticides. It possesses the following features: being used in a small amount, stable to light, metabolized and excreted in mammals quickly, having broad-spectrum and low-residue, effective to insects which is resistant to organic phosphorus, and mainly used to control the agricultural insects in cotton fields, vegetable plots, fruit trees and tea, as well as hygiene insects, used in fisheries production for killing parasites as well. Therefore, it is one of the flagship products of pesticides in the world, with annual sales of more than 250 million U.S. dollars. However, since they have been used for a long term, pyrethroid insecticides are facing a fatal problem, i.e. insects have become severely resistant to them (edited by Zhengming L I, Huazheng YANG; Canping D U, Lusheng L I U, Heng ZHANG, “The development strategy of the 21 century Organic Chemistry”, Chemical Industry Press, Beijing, 2002, p371-380.). The severe resistance to Cypermethrin, Deltamethrin, and Fenvalerate which are used mainly in agriculture was reported successively in the 1980s and affected their persistent uses (Zhengjun SHAN, Zhonglin Z H U et al. Pesticide Science and Administration, 2000, 21(5), 22). Pyrethroids used in hygiene, such as allethrin, tetramethrin, and the like, are also facing the same problem. (Xiaopeng C A O, Caihong Y U, Xiwu G A O, Chinese vector Biology and Control journal, 2004, 15(2), 105). For example, dengue fever and encephalitis prevailed in Taiwan, Hong Kong, Guangdong, Fujian and other areas in recent years, and it was reported that the resistance of the local mosquitoes to pyrethroid insecticides was the root causes for these diseases. Moreover, this problem has a trend of continued spreading. In order to deal with the insects, such as mosquitoes which is more and more difficult to kill, producers have to keep on increasing the pesticides' concentration, and the trump pesticide, Deltamethrin with moderate toxicity (the acute toxicity for rat by oral administration LD50 70˜140 mg/kg), which used to be only applied for agriculture, is now also used in the home. However, this will lead to a more vicious cycle, further affecting its sustainable use. In the other aspect, the major product of pyrethroids, Deltamethrin, is recently under suspicion to have a teratogenicity and mutagenicity (Weihua ZHENG, Jianzhuang ZHAO, Deying M A, Shicong H O U, Transaction of Agriculture college of Beijing, 2004, 19(1), 77). Another major product of pyrethroids, Cypermethrin, is recently under suspicion to be an incretion interferent (i.e. an environmental hormone) and is listed by the US Our Stolen Future website (Ren REN, Jun HUANG, Safety and Environmental Engineering, 2004, 11(3), 7). It is believed to be an estrogen which can interfere the procreation function of humans and animals.
2,2-dimethyl-3-(2-chlorovinyl)cyclopropane carboxylate, 2,2-dimethyl-3-(2-bromovinyl)cyclopropane carboxylate, 2,2-dimethyl-3-(2-fluorovinyl)cyclopropane carboxylate, (referred to as meta-halo pyrethrate hereafter) such as α-cyano-3-phenoxybenzyl-2,2-dimethyl-3-(2-chlorovinyl)cyclopropane carboxylate, α-cyano-3-phenoxybenzyl-2,2-dimethyl-3-(2-bromovinyl)cyclopropane carboxylate, are only detected in minute quantities in the biodegradation or photodegradation products of Cypermethrin and Deltamethrin and have never been efficiently used. Elliott has synthesized and pointed out that the insecticidal activity of the following α-cyano-3-phenoxy benzyl meta-halo pyrethrate was lower than that of the corresponding α-cyano-3-phenoxy benzyl di-halo pyrethrate (Pestic. Sci. 17, 1986, 708.):

Demassey, Jacques et al. has generally disclosed a compound with following formula in their patent application (CN1044650A, EP-381563):

and this reference has specifically disclosed the following tetrafluorobenzyl meta-halo pyrethrate:

However, all of these compounds have such low insecticidal activities that they can not meet the requirements on the pyrethroids in the public hygiene, in controlling vector insects and protecting agriculture plants. In addition, their alcohol part is polyfluorobenzyl alcohol, which is difficult to be synthesized and expensive. In fact, none of the meta-halo pyrethrate pyrethroids has been commercially produced.
In recent years, the factors, such as population growth, and the like, cause shortage in food, which further causes a global rise in foodstuff price; and, the global warming that expedites the propagation of harmful insects such as mosquitoes. It results in the spreading tendency of the infectious diseases, such as ague, dengue fever, and West Nile virus, which are spread by the mosquitoes. The survival of humans faces a new challenge, and human beings need more and better pesticides to guarantee the foodstuff production and people's health. In the other hand, a lot of attention has been paid to the food safety problem caused by residual pesticides. Therefore, the Europe Union, Japan and the other countries have adopted the most severe standard so far on the maximum residue limits for pesticides (MRL) in foods. For example, the MRL of fenvalerate in teas reduces from 0.1 mg/L in 1999 to 0.05 mg/L. Therefore, there is an urgent need to develop a novel pesticide with stability, high activity, quick efficiency, low resistance and liability to degradation.